getScheme

Get the primary scheme associated with this namespace. Subclasses must
provide an implementation that returns a non-null scheme
identifier. Note that the returned scheme should not contain the
Namespace.SCHEME_SEPARATOR (\":\").

An empty two-dimensional array (new Class[0][0]) is the default returned
by this abstract superclass. This means that the Object [] passed to
Namespace.createInstance(Object[]) will be ignored.

Subsclasses should override this method to specify the parameters that
they will accept in calls to Namespace.createInstance(Object[]). The rows
of the returned Class array are the acceptable types for a given
invocation of createInstance.

The above means that there are two acceptable values for the Object []
passed into Namespace.createInstance(Object[]): 1) a single String, and 2)
two Strings. These would therefore be acceptable as input to
createInstance: